In the art of making roofing shingles and tiles for exterior application in the building industry, various approaches have been made toward making shingles and tiles that are manufactured, but give the appearance of being made of traditional natural materials, such as wood cedar shakes, tiles, slate, etc.
In many instances, such shingles and tiles are made of bitumen coated mat having granules on the exterior surface, with the granules being provided in various designs, shades, color configurations, etc., to yield various aesthetic effects.
It is also known, in making roofing shingles and tiles, to mold them to the desired shape by various molding techniques. The materials that are used in such molding techniques usually include inexpensive filler material, in order to achieve low production costs.
Some such filler materials can be various waste products, such as carbon black, recycled rubber and tire crumb, coal fines, pulp and paper waste and other inexpensive materials.
Such products are often made by molding multi-component formulations, which comprise blends of virgin and recycled polymers and various low-cost fillers.
The use of large quantities of such fillers reduces the mechanical properties of the ultimate product, however. Additionally, the use of large quantities of fillers limits the color variations that are possible in the products and makes the processing of the formulations into shingles and tiles very difficult.
Typically, roofing shingles and tiles made of such material having waste for filler do not provide good weather resistance for the products. Additionally, the warranty periods that can reasonably be provided for such products tend to be short in duration.
Furthermore, such building industry roofing products have relatively low impact strength, especially at low temperatures. Insofar as their available colors are concerned, such tend to be limited to the colors gray and black.
Additionally, molding operations tend to be capital intensive, with relatively high manufacturing costs, although molding techniques do provide a high level of definition or dimension control. Also, there is a disadvantage to molding techniques, in general, in that the length of the cycle for injecting material into the mold, molding to the desired shape, and ejecting the shape from the mold is largely a function of the time required to cool the molten thermoplastic material before it can be removed from the mold. However, the temperature of the thermoplastic material must be sufficiently high that it can flow and fill the cavity within the constraints of the material and equipment (i.e. material characteristics, melt pressures, mold clamping pressures, etc.). While modifications can be made to the materials to help the flow characteristics and thereby lower the required melt temperature, and while improvements can be made to the mold to increase heat transfer and removal, cooling remains the longest part of the cycle for these processes. In order to achieve the necessary cooling, the time required causes a lengthening of the manufacturing cycle, which increases the capital costs of investment in molds and machinery for a required output, thereby substantially increasing manufacturing costs.